Pediatric Fundamentals Growth and Development

1. Pediatric Fundamentals Growth and Development Drs. Greg and Joy Loy Gordon January 2005

2. Pediatric Fundamentals - Growth and Development Maturational change in form and function Prenatal Growth Gestational age (wks) Mean birth wt (Gm) 25 850 28 1000 30 1400 33 1900 37 2900 40 3500 Postnatal Growth Birth weight doubles by 5 months triples by 1 year Birth length doubles by 4 years

3. Pediatric Fundamentals - Growth and Development Maturational change in form and function Percent body water Term newborn 80 1 year old 70 Adult 60 Surface area:Weight premature > full term > infant > child greater surface area greater evaporative heat loss rapid hypothermia if unprotected Girls Boys Puberty onset 11 years 11½ years Peak growth Tanner stage 3 Tanner stage 4

4. Pediatric Fundamentals - Growth and Development Fluid requirements Metabolism of one calorie of energy consumes one ml of H2O, so fluid requirements thought to reflect caloric requirement: Body weight (kg) Calories needed (kcal/kg/day) = Fluid requirement (ml/kg/day) 0-10 100 10-20 1000 + 50/(kg>10) > 20 1500 + 20/(kg>20) Dividing by 24 (hours/day) yields the famous 4:2:1 Rule for hourly maintenance fluid: 4 ml/kg/hr 1st 10 kg + 2 ml/kg/hr 2nd 10 kg + 1 ml/kg/hr for each kg > 20

5. Pediatric Fundamentals - Growth and Development Airway/respiratory system Gas exchange first possible approximately 24 weeks gestation Surfactant production appears by approximately 27 weeks produced of Type II pneumocytes exogenous form available Number (and size) of alveoli increase to age 8 years (size only after 8 years) First breaths of air pneumothorax or pneumomediastinum less than 1% several hours to reach normal lower lung fluid levels some expelled during birth canal compression transient tachypnea of newborn (TTN) increased incidence after C-section

6. Pediatric Fundamentals - Growth and Development Respiratory rate/rhythm pauses up to 10 seconds normal in prematures without cyanosis or bradycardia Age (years) Normal Rate 1 - 2 20 - 40 2 - 3 20 – 30 7 - 8 15 - 25 Obligate nose breathing especially prematures able to mouth breath if nares occluded 80% of term neonates almost all term infants by 5 months

7. Pediatric Fundamentals - Growth and Development Airway differences – infant vs adult epiglottis and tongue relatively larger glottis more superior, at level of C3 (vs C4 or 5) cricoid ring narrower than vocal cord aperture until approx 8 years of age 4.5 mm in term neonate 11 mm at 14 years

8. Pediatric Fundamentals - Growth and Development Cardiovascular system In utero circulation placenta -> umbilical vein (UV)-> ductus venosus (50%) -> IVC -> RA -> foramen ovale (FO) -> LA -> Ascending Ao -> SVC -> RA -> tricuspid valve -> RV (2/3rds of CO) -> main pulmonary artery (MPA) -> ductus arteriosus (DA) (90%) -> descending Ao -> umbilical arteries (UAs)->

9. Pediatric Fundamentals - Growth and Development Cardiovascular system Transition to postnatal circulation Loss of large low-resistance peripheral vascular bed, the placenta (UV, UAs constrict over several days) With first air breathing marked drop in pulmonary vascular resistance with greatly increased pulmonary blood flow LA pressure > RA pressure closes FO Elevated PaO2 constricts DA hours to days Hgb F impairs postnatalO2 delivery Higher newborn resting cardiac index with decreased ability to further increase

10. Pediatric Fundamentals - Growth and Development Cardiovascular system Normal murmurs up to 80% of normal children vibratory Still’s murmur basal systolic ejection murmur physiologic peripheral pulmonic stenosis (PSS) venous hum carotid bruit S3 Murmur only in diastole = abnormal

11. Pediatric Fundamentals - Growth and Development Gastrointestinal notes Gastric pH higher at birth; decreases over several weeks Young infants diminished lower esophageal sphincter tone 50% have daily emesis (usually remits by 18 months) more show reflux if esophageal pH monitored only 1 in 600 develop complications of reflux Physiologic jaundice Colic < 3 months Umbilical hernia common frequently resolve spontaneously Teeth primary: 7 months to 2 or 3 years permanent: 6 years to 20 years

12. Pediatric Fundamentals - Growth and Development Renal system Urine production begins first trimester Newborn GFR low (correlates with gestational age/size in prematures) rises sharply first 2 weeks adult values by age 2 years limited concentrating ability (600 vs adult 1200 mOsm/kg) ability to dilute urine relatively intact

13. Pediatric Fundamentals - Growth and Development Hematologic system Infant Hgb F – higher O2 affinity Hgb A production largely replaces Hgb F by 4 months Hgb/Hct decrease to nadir at about age 2 months exaggerated in prematures (low total body Fe stores) Blood volume (ml/kg) Prematures 105 Term newborn 85 Adult 65

14. Pediatric Fundamentals - Growth and Development General pharmacotherapeutic note: On a per kg basis compared to adults Expect lower doses in infants and Higher doses in children

15. Pediatric Fundamentals - Growth and Development Neuro notes Nervous system anatomically complete at birth except: Myelination rapid for 2 years complete by 7 years Posterior fontanelle closed by 6 weeks Anterior fontanelle closed by 18 months Primitive reflexes disappear in few months

16. Pediatric Fundamentals - Growth and Development Developmental pediatrics History and physical notes Newborn – pregnancy and delivery Infancy – developmental milestones Toddler – poor localization of symptoms and very suggestible (e.g., pharyngitis or pneumonia presenting as abdominal pain or distress) Older child – involve in discussion/decision Preadolescent and older – consider interview without parents Exam opportunistic approach in infants and young children observation essential distraction useful

17. Pediatric Fundamentals - Growth and Development

18. Pediatric Fundamentals - Growth and Development

19. Pediatric Fundamentals - Growth and Development Developmental pediatrics Approach to patient depends on stage of development Stranger anxiety 7 months 25% 9 50 12 75 Toddlers magical thinking (belief that own thought or deed causes external events) temper tantrums (aggravated if tired, ill, uncomfortable) Toilet training ability develops by 18 months usually complete by 2 to 3 years (day before night) bedwetting 15 - 20 % at 5 years with gradual decrease to 1% at 15 years 6 -11 years - concrete operations phase can consider different points of view develop explanation based on observation beginning logical reasoning but still tend to dogmatic 11 and older - development of abstract thinking Adolescent - increasing need for autonomy, participation in care

20. Pediatric Fundamentals - Growth and Development For more info regarding age-related preparation of the pediatric patient for anesthesia see: http://metrohealthanesthesia.com/edu/ped/pedspreop3.htm